Not all feedback and discussion revolve around creative materials. For discussions around market locations, brand positioning, competition, and other topics, people typically turn to email.
Email is great, most of the time - as long as there aren't any large files attached, and as long as the conversation is short and only between two people.
Besides the security and reliability issues, the most significant issue with communicating via email is ensuring all team members have a consistent and up-to-date view of the evolving discussion. Back and forth emails among groups of people are hard to follow, increasing the likelihood of communication breakdown.
Have you ever wondered what the other people in your email discussion are seeing? This screenshot shows some of the many possible formats email recipients might see. (Names blurred to protect the innocent.)